I finally found a forum for TPI's only, so lets see what you think, I've been trying to figure this out for over a month.
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After completing the swap from TBI to TPI on my truck, I'm experiencing massive amounts, 6-10 degrees of KR on just light accelleration. I've adjusted the timing from 10 BTDC to 4 ATDC and it doesn't seem to make much difference, besides killing any performance when at 0 or below. I could hear it pinging, so it's not false knock. O2s are in the 860-950 range so it has plenty of fuel. Even removed the cat thinking it may have been clogged, no help.
Changed the EPROM and the entire ECM, no help.
I can't think of anything else to check...
I am using the stock cam/heads, some have told me I should try L98 heads and a TPI cam, but others say it should work fine, I know every vendors that sells the TPI says it will work fine.
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Anyone with any other ideas??? I've even filled the tank with 101 octance race gas, no help.
Thanks

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Rob
High Performance & Party page
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89 TTA #426 20th Anniversary turbo 3.8 bone stock
94 Silverado Tuned Port Injected
87 Grand National- lil' ole V6, highly modded
95 Trans Am Conv.- LT1

 

Is it actually knocking or just the computer thinking it is?
If its just the computer, that could be fun to track down. I'd be wondering what knock sensor and ESC you are using.
If its actually knocking, look for vacuum leaks. Is it the MAF or SD system? The MAF setups like to leak where the cold start injector is, if you are using one.

 

Its a SD system, and the computer module is from a '92 IROC. Not sure about the knock sensor, its the one that came with the TPI setup. I can hear it pinging on occassion, so I don't think it is false knock.
Oh yea, it pulls around 18 inches of vacuum at idle.

[This message has been edited by 2QUIK6 (edited January 19, 2001).]

 

You can't go necessarily by the O2 sensor, they are not accurate enough to properly gauage WOT.

Whose eprom is it? It may be the eprom has too much advance built into the spark table. BTW, your base s/be 6*BTDC.

An injector imbalance (a few poor ones) may be causing some cylinders to run lean while others are rich. What is your fuel pressure BTW? You may have too high a fuel pressure while your fuel pump might be a bit weak. This too could cause a lean condition at certain loads.

 

FP is at 46# at idle with hose off. Putting on an adj. tomorrow so I can mess with that.
Too much FP could cause a lean condition??
The pump is a brand new stock replacement that came with the setup.

 

Only if you are exceeding the fuel pump. At 46, you should be find. Its when you get into the 50s (>55) that you could have a problem.

If you were to have a problem with 46, your fuel pump would be the problem. How's your fuel filter BTW?

And who's eprom?

 

Fuel filter is brand new, as is the fuel pump. Pressure stays in the 46-48# range at WOT. This is a completely stock TPI application so extra fuel should not be needed. I'm going to install an adj FP reg today and crank it up a little and down a little to see what happens, timing currently is at 2 BTDC base to reduce detonation some.
I've tried different eproms, a stock one Andrew at AKM supplied me, and then Fuel Injection Specialities have tried a few, but they are idiots now that the owner/programmer passed away.
Thanks for the help so far.

 

Personally, based on what your are saying, I don't give you much luck. Your fuel pressure is in the higher range but it is acceptable, your fuel pump is new as well as your fuel filter.

The only things I can think of is either an injector imbalance, an overly sensitive knock sensor, something flaky with the ESC (Electronic Spark Conrol) system, the aftermarket eproms have too much advance or a vacuum leak somewhere.

Do you have a scan tool by any chance or know someone that has access to one? If not, consider renting Diacom+ from TPIS. They use to have them available for $50.00/week. It will at least help you diagnos when it is occuring and you could save the captured file to give to someone to look at. You could convert the GDF file that Diacom+ creates to DBF (with the Diacom Translate command) and then fire it off to people. The DBF can be read by a variety of programs, including Excel.

It may be one of the aftermarket chips really advanced it and limited the maximum knock, thus causing the knock to be heard. I found that if knock occurs at even 2,000 rpm due to the advance coming in too quick, it can trigger audible knock and penalize you through out the rpm range.

I tracked a knock problem on my car to this very thing. Even the GM eprom caused me to have knock at low rpm which screwed me throughout the rpm range. I just slowed down the rate of advance coming in, and it went away and I found I could add even more advance at the top part of the rpm...where you want it.

You should find 87z-ya in San Antonio TX. He is interested in finding someone in TX that wants to get into eprom burning to work together with him. Do a search on his name (I think he recently made a few posts in the PROM Board) and drop him an e-mail.

Misery loves company.

 

By the way, do you have the correct Knock Sensor? There is supposedly two different knock sensors for these cars. One for the 305 and another for 350s.

You'll probably still have some knock (though inaudible) until you tweak the Spark Tables to slow down the advance (or wherever Diacom+ says it is being triggered).

 

BTW, what spark plug and gap are you using and have you tried a colder heat range of spark plug?

It may help to reduce some of the detonation and you basically risk just fouling plugs more often. In the old days, we seldom got more than 10,000 miles out of plugs. People are just spoiled not having to change them only once a year.

Give it a try if you haven't.

 

I am still using my 305 knock sensor in my 350 with no problems. The 305 and 350 knock sensors do have different part numbers.

 

I do have a scan tool, DataMaster. Not sure about the ks, it looks just like the one that was originally on it in the TBI setup, but I replaced it with the one that came with the TPI.
I put on the adj fp reg, base was at 46#, so I started at 44#, had more knock than before. Cranked it to 50# base hose off, and it did slightly better, not as much knock on those soft accels.
Cranked it to 55#, and I think it had more knock than at 44#, WTF??
But while adjusting the pressure, I think I can hear a slight rod/lifter knock on the passenger side, right where the knock sensor is, I think that may be my problem, serious work ahead if so....
I'm going to try a test by hooking up my "old" sensor to the wire and wrapping it up in foam, so it won't detect any knock and drive around and see how it feels.
Also will pull the spark plugs and get a reading from them...they are AC R45TS gapped at .38, I've tried R43TS and they didn't help either. I've also filled the tank with 101 race gas, and that helped slightly, so I'm beginning to think its the rod or lifter knock...
Thanks guys

 

No one mentioned EGR as a possible cause. Are you running EGR on your engine? Malfunctioning EGR operation can cause engine knock.

 

I originally thought about the EGR, it was not epuiped with one. So when FIS had it, they put one on at my request, well, they didn't run it through the ECM, its just hooked to a vacuum line so its always on, should help out for knock either way, but it didn't help either. I checked it to be sure it was working/operational and it is.
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All spark plugs look exactly the same, dry, and a light brownish/red in color, like brown spray paint primer color.
Unhooked the knock sensor, and no, its not false knock, with the sensor unhooked, I can hear the pinging, so its not the rod knock.
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At steady cruise speed of 70 mph, scan tool is showing SPARK ADV of 30-31 degrees, and I'm getting constant Knock Retard of 3-5 degrees!!
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Any more ideas??? I'm going to take it to a programmer next weekend see what he can do/find...
Thanks

 

Try a colder heat range of spark plug.

 

I've tried the R43TS, didn't seem to help either. Should I try even colder? I didn't try since it didn't seem to make a difference.
The knock is getting worse at highway cruise speed, I'm starting to see 8-10 constant, but I can push the pedal further at it gets less, 4-5?? As you can tell, I've spent almost every free minute the last 2-3 months trying every thing I can think of...
May crap the short block and start over soon...very frustrating

 

How much compression do you have and what oct gas are you using? Try some oct boost with some prem gas and see if that helps any.

Steve

 

I thought I mentioned I filled the tank with 101 unleaded race gas, but still got knock, but was about 3-4 degrees less than with 92 pump gas.
Compression, hmmm, I did a check and got 170-180psi cranking compression on each cylinder. One shop thought that 180psi was increadible and too high for a completely stock motor, but this is the motor that came in the truck and I've had it since new. They felt it should be around 125. Others felt that it was no big deal unless higher than 200. Also, ran a ton of top end cleaner thru it to clean out any carbon.
Guess I should post a compression check poll...
Thanks, might be back on to something.

 

you say you had what you thought was a rod or lifter knocking? nut iread and you eliminated the rod possiblity, so, could the lifter be broke or could you just need to re-run the valves? (set rocker tightening) email me agian with any questions on setting the valves! it sound like a lifter prob! check the exhaust! is it glowing red when this happens? just curious! if the lifter is broke then it will sense detonation. and thats bad, you get retard of timing and that damn pinging over and over on tpi email me again and let me know i'll respond about 10:30 or 11:00 monday 22nd night!(after work )


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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!

 

It like this thing will not run the same way twice, but here's the latest.
Put in a 160 thermostat and plugged up the vacuum tube from the VC breather and carbon canister. Now it gets very little detonation in 1st and 2nd gear, only about 3-4 degrees on heavy accel, but highway cruise, its way up there, 12-15 degrees at cruise 70 mph!!
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So, if the lifter was bad, I think it would run like crap in 1st and 2nd, but its real strong. I'm beginning to think its all in the programming and timing tables. I'm going to let a guy at CSS Motorsports take a crack at it next week. I'll let ya'll know what happens.

 

Well, I checked into ALL the possibilities according to my GM Shop Manual and these are the main areas they suggest checking. I believe we have covered almost everything:

1) Cooling system - Low coolant, loose belts, proper T-stat range, good CTS (Coolant Temperature Sensor). If you believe your cooling system is operating properly and you are getting proper readings from you CTS...cross this one off.

2) Fuel system - Proper working fuel injectors within specifications, proper fuel pressure range, fuel quality.

3) Ignition system - ESC functioning properly, timing, distributor and rotor.

4) Other - EGR not opening, Carbon buildup, proper transmission shift points, TCC operating, proper heat range of spark plug, oil entering the combustion chamber (especially valve seals), proper mechanical parts, loose valve train (chain, lifters, rockers), proper memcal.

I sounds that you have hit a lot of the basics already and possibly only a few of the "hard ones left".

BTW, what modifications have you on the engine? What compression ratio, heads, cam, etc. Please describe everything about your motor (age, miles, rebuilds, parts, etc).

I read your post about your cylinders psi. On a stock motor with 9.5:1, that would be fine with the stock cam (I'll assume). But if you have bumped up the compression, you will need to bleed off some of the pressure with a wider LSA. Also, who's eprom are your running? Stock GM?

[This message has been edited by Glenn91L98GTA (edited January 22, 2001).]

 

Everything is stock original on the motor with almost 100k. Chip has been swapped several times with no help, now its whatever FIS left in with alot of timing taken out, but maybe not taken out in the correct table frames??. I can see the CTS switch changing from 0 to 1 on the scan tool, so its ok.
Thanks, keep the ideas coming

 

On the highway cruise, I would lean towards the EGR's not functioning. What is the total spark that your scan tool is showing that the engine is attempting at highway cruise. I get 36*-38* no problem except up the longest of grades where my MAP climbs to 80 kpa @ 70 mph. And even then, the amount of retard is .5-1.0*...the sensor just doing its job like it is suppose to.

Maybe if you disabled the EGR in the eprom it may help. You probably will have to back the part throttle timing back a little, but not much. Or get the EGR fully functioning at the ecm.

Your WOT results are acceptable, again a few degrees is not bad and it just means the knock sensor is doing its job. You only need to get concerned with WOT if the knock retard is going over 6-8* IMO because then you are loosing performance if it is trying to give you 34*-36* total advance. You should be able to handle 30*-32* total advance with virtually no knock and 34-36* with only a few degrees.

 

does it knock at idle at all? if it is detonation i would say that you have a bad injector, but im kinda convinced that what your hearing is not detonation. cause if it was an injector it would run like crap. since the motor has 100k miles on it id look to make sure its not a lifter or a rod knocking. and if it is a rod, you might as well rebuild the engine. rod or lifter noises that are loud enough can set off the knock sensor.

 

Based on what 2Quic6 is saying, I have to agree with him that if it was mechanical, then it would happen through out the powerband at all rpms, and WOT. It seems to be happening only at part throttle (the rest seems to be within acceptable tolerances now). That leans me to the EGR because this is where it has the greatest effect.

Earlier in the post, 2Quik6 mentioned that the EGR is not being controlled by the ecm, which makes me think that this is the source of his problems.

A bad injector would show more at WOT than any place else. At part throttle, the pulse width is short enough that it would have minimal affect and show more at part throttle load (up hills) and especially @ WOT when the pulse width was the longest.

 

Nope, no knock is detected at idle, even revving the motor in PARK doesn't produce any knock retard. At highway cruise, the spark adv being commanded is about 30-31 degrees.
EGR is just hooked to a vacuum line, and not to ECM and is programmed out of the ECM. Yep, leaning toward the ECM not being programmed accordingly for what I'm seeing.
If it was rod knock that was loud enough, I think I would see some knock while revving in park, but maybe not since there is no load on the engine.
Thanks, guess we'll see what can be done next week.

 

Quik, is the 30* your TOTAL Advance or your "relative advance" (Total Advance - Spark Retard = Base timing + relative spark advance)...don't ask me WHY it works that way...it just does. I am now paying more attention to the "relative advance" as it has the spark retard factored into it.

I guess GM wants the Total Advance to be the amount of advance the ecm is TRYING to give you...but you must deduct the Spark Retard to calculate your effective total advance or add the base to your relative.

 

You mention the EGR being hooked directly to a vacuum line...

Question, does this line have vacuum all the time? If so, then the EGR valve is not functioning...if you had EGR at idle, the motor would idle horribly, if at all.

Could be the vacuum line is for looks, and you're not getting any EGR.

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And thinking about this a little more...the EGR vacuum is controlled through the solenoid (I think) so if the solenoid is not energized, no vacuum will operate the valve...rendering it disabled anyway.

I'll have to pop the hood tomorrow to see where the vacuum is applied to.

[This message has been edited by 8Mike9 (edited January 22, 2001).]

 

Glenn, I think what I'm seeing on the scan tool is "relative" spark adv that is being commanded. Only reason I think that is because I see the "spark adv" value on the scan tool go down a corresponding amount equal to what is being "retarded".
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8mike9, the EGR is just hooked to a vacuum line, no solenoid at all. If I push up on the diaphram while idling, the engine almost dies so I assume it is functional,....but that's a good point, at idle is the highest vacuum so it would open it, never thought of that, so maybe its not working at all!
I do know that the EGR only has a vacuum tube going to it on any set up, but the vacuum line is hooked thru a solenoid that is controlled by the ECM to open/close the vacuum line to operate the EGR under only certain conditions. There are no wires going to the EGR, not that I've ever seen on any of my cars.
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But I wonder why the EGR is not wide open at idle since there is no solenoid??? Anybody know how that works? Or maybe its not working at all. hell the diaphram may be fried...

 

The vacuum line on your egr valve may be hooked to "ported" vacuum. (i.e. as rpm increases, so does vacuum.) Where on the engine is the line hooked? Obviously, on end is on the valve itself, where does the other end go?

 

ploegi, it connects to the vacuum line hook up under the bottom drivers side corner of the TPI throttle body. Is that one that way??
I'm out of town right now or I could check it to see if it has any vac at idle.
Didn't realize there were some that increased vac as rpm increased. But that explains why the pass. valve cover tube hook up had hardly any vacuum on it at idle and it hooks to the top pass. side large tube on the TB.
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I think its probably working because when I had the TB off, I noticed the EGR holes right behind the TB had some black soot stains smearing out of them.

[This message has been edited by 2QUIK6 (edited January 23, 2001).]

 

Thats where the vac line should be. If you don't have a soilnoid inline it won't make any difference when its warm, but EGR is supposed to be stopped when coolant temps are low to speed warm-up. I don't think it matters much in this respect.

Another point for the computer guru's is that heat sensing switch that signals EGR flow to the ECM. Would this signal the ECM that EGR is flowing when it shouldn't(cold). What would the ECM do then?

If the switch isn't hooked up the ECM would think EGR is never occuring. What effect would this have.

I'm not sure if this has anything to do with your prob but I always wondered why the ECM needs to know if its flowing when it's in direct control of the solnoid. Just for the dam SES light or what???

 

The ECM controls the EGR and can vary the EGR's functioning from 0 - 100% based on a variety of factors. It does not just either work 100% or not work at 0%.

I haven't dived too much into the hack, but I believe that it also gives a little more timing when the EGR is functioning.

 

Im sure fis hooked up the egr to a ported vacuum switch. If you have a adjustable advance timing light , use it to check the advance while est is hooked up, and see if it mirrors what the scan tool is reading. It sounds to me like maybe your distributoror something else in the esc circut is bad. The computer will still send a reading of 30 deg to your scan tool but you might not be actually getting it. Of course I could be totally off but it wouldnt hurt to check.

 

Hey 87Z-ya, I see you're in SA, make sure you don't go to FIS, they are idiots since the owner passed away. Yea, it is hooked to a ported vac, checked it today when I got back in town.
Distributor and ECM and wiring were suposedly swapped but it did no good. I'll check the timing more closely tommorow with the light, but it appeared to be advancing at idle like it was indicating on the scan tool. Have to move my laptop into the engine compartment tommorow and check at other rpms.
Good idea.
Thanks

 

Fis is still ok if you talk to the right people. I know they poke your eyes out though , it was a shame that he died. Its to bad we cant download the memory of someones brain after they pass cause he knew his ****.

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87z 383,afr 190's, crane hyd roller(224/230-.509/.528,112 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, strange 12 bolt, tremec 5spd, , 1,3/4" slp headers.

 

I won't be back to FIS, they said they were doing one thing, then when I'd call back, another guy would say something completely different. When I went to pick up my truck, I brought my laptop and DataMaster, a couple of the guys acted like they had never seen a scan tool, and they tune these things!??? And one of them was the guy that worked on my darn truck! Anyway, I'm in the process of disputing a few charges that I'm now having to pay someone else to do right the second time around, like the EGR, that they told me they were in the process of wiring up to the ECM, I get there to pick it up, and its not wired into the ECM at all!
It is this reason that I absolutely hate to let anyone else touch my vehicles, they usually don't know hardly anymore than anyone else. Only as a last resort!

[This message has been edited by 2QUIK6 (edited January 25, 2001).]

 

Makes me wonder which eprom they used and what modifications they did to it.

No, I agree. Sure doesn't sound like they did any tuning at all...probably go some generic eprom (or worst, an ADS) and just switched of the EGR (or whatever).

The only time I let someone else work on my car is when it is a "simple no brainer" but dirtier than hell or requires a lot of hands. And even then, it "stresses" me out to have someone "touch it".

 

I heard that the knock sensor must not be over tightened in the block. if you do it can be damaged. maybe the sensor is no longer functional.